This invention relates to an attachment for a direct drive gasoline or electric powered portable chain saw, and more particularly relates to an attachment for such a chain saw for delimbing, thinning, pruning and brushing.
Several problems arise when a portable chain saw is put to use for which it was not primarily designed, for example, for cutting wood of relatively small diameter (e.g. two inches or less). In addition to the ever present danger of kickback, it may be difficult to hold a sapling or small branch steady to enable the teeth of the chain to cut. Moreover, when using a chain saw in brush or closely spaced trees, there is a difficulty in accurately cutting without damaging adjacent brush or trees.
To facilitate such operations, straight prongs, of flat cross-section secured to the flat of the blade at varied locations thereon, and protruding therefrom in various orientations have been proposed in the past. A prong extending forwardly parallel to the longitudinal axis of the chain saw blade is described and illustrated in Robinson U.S. Pat. No. 3,680,607 issued Aug. 1, 1972; a prong protruding diagonally, laterally from a middle location along the length of the saw blade is described and illustrated in Graves, et al Canadian Pat. No. 585,268 issued Oct. 20, 1959; a similar type of prong, positioned towards the front tip of adjacent chain saw blade is described and illustrated in Canadian Pat. No. 524,343 of Budd issued Apr. 24, 1956. Haddan U.S. Pat. No. 2,925,105 issued Feb. 16, 1960 describes and illustrates a straight, flat prong for either central or tip positioning on a blade, the angle of which is adjustable. The prong has two spaced sides, the chain of the saw passing through a space between the sides. Multiple blade attachments are described and illustrated in Hayden U.S. Pat. No. 2,642,901 issued June 23, 1953 and Jakku U.S. Pat. No. 2,698,034 issued Dec. 28, 1954.
While such prior art devices may be effective for limited purposes, their applications are restricted by the angle of the prong, the location and orientation in which the prong is attached to the blade, and the construction of the prong itself. For example the space between the double sided prong, between which the chain runs, would permit brush to build up and become clogged therein if it were used for brush cutting or cutting of other relatively fine vegetation. Some prior art devices provide an attachment means to the blade which has a front edge surface positioned normal to the longitudinal axis of the blade. This creates an abuttment to material being cut to prevent such material from passing freely over and beyond the blade. In operations using most of these devices there is no physical means to limit the size of material being cut and, during cutting, mechanical guiding of the material being cut is either partial or absent. Finally, with the vibration involved in operating a chain saw particularly in confined quarters when pruning or the like, the flat prongs of such prior art devices provide a sharp edge which may rub against adjacent foliage and cut or damage such foilage during the cutting operation.
It is an object of the present invention to provide a chain saw attachment which will be versatile in enabling the chain saw to effectively delimb, thin and prune foliage over a wide range of conditions and sizes. It is a further object of the present invention to provide such an attachment which will enable such activity to be carried out with minimal damage to adjacent foliage.